Abstract

Dielectric properties of (BST) thin films, which were prepared on silicon-based substrates by ion beam sputtering and postdeposition annealing method, were systematically investigated in different electrode configurations of metal-insulator-metal and coplanar interdigital capacitors. It was found that a large dielectricanisotropy exists in the films with better in-plane dielectric properties (higher dielectric permittivity and tunability) than those along the out-of-plane direction. The observed anisotropicdielectric responses are explained qualitatively in terms of a thermal strain effect that is related to dissimilar film strains along the in-plane and out-of-plane directions. Another reason for the dielectricanisotropy is due to different influences of the interfacial low-dielectric layer between the BST film and the substrate (metal electrode).